In a multicore system that includes storage units and CPUs in plural, multiple CPUs may attempt to access a single storage unit concurrently. As a countermeasure to prevent such a situation, it is conceivable that processing being performed while switching the storage units that are accessed.
For example, according to an existing technique, tasks that access a disk drive are grouped and the threads thereof are executed in series according to a task list to prevent contention at the disk (see, e.g., Japanese Laid-Open Patent Publication No. H7-104939). According to another technique, with respect to a storage access request having a time limit, if writing to an intended storage unit is not completed within the time limit, data is written into another storage unit and then transferred to the intended storage unit later (see, e.g., Japanese Laid-Open Patent Publication No. H10-91357).
According to another technique, in an image data search system, a multi-optical disk apparatus and a single-optical disk apparatus are connected and, image data is temporarily registered in the single-optical disk apparatus and then transferred to the multi-optical disk apparatus, thereby preventing access contention for the image data even if a registration request and a search request for the image data occur at the same time (see, e.g., Japanese Laid-Open Patent Publication No. H3-018976). According to yet another technique, in a multiprocessor, an arbitration logic unit is disposed that determines types of access requests to an HDD and that sets a different address space for each of the types to control the access requests such that any process may be executed first when access contention occurs (see, e.g., Japanese Laid-Open Patent Publication No. 2009-187327).
However, in the techniques described in Japanese Laid-Open Patent Publication Nos. H7-104939, H10-91357, H3-018976, and 2009-187327, access scheduling for storage and task scheduling of OSs are performed independently and therefore, access contention with respect to storage may be expected to occur among multiple CPUs when the CPUs attempt to access the storage. The occurrence of the access contention reduces access performance. With the technique described in Japanese Laid-Open Patent Publication No. 10-91357, since only access scheduling for the storage units is considered without coordination between the access scheduling of storage units and the task scheduling of OSs, access contention for one storage may occur when multiple CPUs execute respective tasks.